Turbocompressor having a radial diffuser

ABSTRACT

881,882. Centrifugal pumps and compressors. SULZER FRERES S.A. Dec. 8, 1958 [Dec. 23, 1957], No. 39514/58. Class 110 (1). A centrifugal pump or compressor comprises a first ring 4 concentric with the rotor shaft and forming a part of one of the walls of the diffuser of the pump or compressor, the flow cross-section of the diffuser being adjustable by varying the distance S between the diffuser walls by axial movement of the first ring 4, a second ring 13 concentric with but axially spaced from the ring 4 and restrained from axial movement, and at least three motiontransmitting members 12 extending between the two rings and arranged at the same angle of akew &amp;alpha; in relation to the rotorshaft, the rings 4, 13 being relatively rotatable and the members 12 being arranged to convert relative rotation of the rings into axial movement of the first ring 4. As shown, the ring 4 is held against push members 11 and the members 12 by a spring 10 and the excess of the pressure between the diffuser walls over that behind the ring 4. Each motion-transmitting member 12 has two spherical ends, one located in a guide passage 14, and the other in a recess 16 in the ring 13. A space 19 containing the motion-transmitting members 12 is sealed off from the diffuser by metal bellows or other sealing members 20 and the first ring 4 has a sealing ring 7. The second ring 13 is rotated by a worm 17 engaging a toothed segment 18 and rotation of the ring will displace the members 12 as in the upper diagram of Fig. 2, which shows the mechanism with the skew angle &amp;alpha; at a maximum. The arrangement described compensates for the increasing percentage reduction in flow cross-section for a given movement of the ring 4 as the distance between the walls decreases. An adjusting screw 22 may be provided for adjusting the effective length of the member 12.

y 1962 K. JASSNIKER 3,032,259

TURBOCOMPRESSOR HAVING A RADIAL DIFFUSER Filed Nov. 26, 1958 INV EN TOR.

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U ite States The present invention relates to a turbocompressor having adiffuser whose flow area can be changed by changing the distance betweenopposite walls of the diffuser, an axially movable annular memberforming part of one of the opposed walls of the diffuser and placedcoaxially of the rotation axis of the compressor being provided for thispurpose.

In a conventional turbocompressor the flow area of the diffuser can bechanged by means of an annular insert in one of the diffuser walls whichinsert is part of a tubular hydraulic piston arranged in a suitablecavity of the pump housing and actuated by means of a pressure liquid.

This conventional arrangement is simple and satisfactory as long as theactuating liquid of the hydraulic piston can be mixed with the mediumwhich is pumped by the compressor. If the two media cannot be mixed andmust be definitely separated, the conventional arrangement isunsatisfactory because it is extremely difficult to completely seal thetubular piston in the cylindrical cavity which has an annular crosssection. A control problem may be added to the aforesaid difficulty.Suppose the diffuser has an axial clearance x and a flow area Q, areduction of the axial clearance by the length a may effect a reductionof the flow area of the diffuser by If the initial clearance of thediffuser is a reduction of the clearance by the same length a effects areduction of the initial flow area by approximately The same controlstroke of the piston produces an increasing reduction of the flow areaat decreasing flow area Q. If the pump is used as a drainage pump whichmay be controlled in a relatively rough manner this controlcharacteristic is unimportant. However, it becomes very important andmay be the cause of control instabilities which are difficult tocompensate, if the compressor forms 'part of a sensitive system, forexample, of a refrigeration cycle.

It is an object of the present invention to provide a compressor havinga diffuser whose flow area can be changed by mechanical means which arecompletely sealed against the inside of the diffuser so that no mediumpumped by the compressor can escape or mix with another medium. In thecompressor according to the invention an annular member which forms partof a wall of the diffuser of the compressor is axially movable but notrotatable and is propped against a ring element, which is coaxial of therotation axis of the compressor and rotatable, by means of at leastthree props which are placed substantially in an imaginary cylindricalsurface which is coaxial of the rotation axis of the compressor. Theinclination of the props relatively to the rotation axis of thecompressor is changed upon rotation of the ring element whereby theannular wall member is axially displaced.

The annular member is preferably urged against the props and the latteragainst the ring element by suitable spring means.

In a preferred embodiment of the invention connecting ice means areinterposed between the annular member and the props, the connectingmeans being guided in the pump housing to move parallel to the rotationaxis of the compressor. These connecting means prevent rotation of theannular wall member and assure a definite guidance in the axialdirection.

It is advisable to seal the portion of a cavity in the compressorhousing containing the link means operatively connecting the annularwall member and the ring element against the operating medium passingthrough the diffuser by means of expansible elements.

A sealing packing may be provided between the circumferential surface ofthe annular member and the respective surface of an annular opening inthe compressor housing in which opening the annular member is axiallymovable. In this way the pressure on the side of the annular memberwhich is remote from the diffuser channel is equal to the staticpressure in the inlet of the diffuser, due to the leakage of medium fromthe diffuser at the inner diameter of the annular member. This staticpressure is smaller than the pressure exerted on the annular member bythe medium flowing through the diffuser so that the annular member isurged to move outwardy and against its props.

A preferred arrangement for the link or propping means between theannular member and the ring element includes props or pin elementshaving spherical ends whereby one spherical end of the pin elementsextends into a suitable recess in the ring element and the otherspherical end of the pin element abuts against the aforesaid connectingmeans and is received in the respective guide in the compressor housing.

The novel features which are considered characteristic of the inventionare set forth with particularity in the appended claims. The inventionitself, however, and additional objects and advantages thereof will bestbe understood from the following description of embodiments thereof whenread in connection with the accompanying drawing, in which:

FIG. 1 is an axial sectional view of a compressor according to theinvention.

FIG. 2 shows the axially displaceable wall member and its actuatingmechanism, forming part of the compressor shown in FIG. 1, in twodifferent operating positions, the actuating mechanism includingadjusting means.

Referring more particularly to the drawing, numeral 1 designates adiffuser having two parallel walls 2 and 3. A portion of the wall 3 isformed by an annular member 4 which is coaxial of the rotation axis ofthe compressor and axially movable so that the diffuser clearance S canbe changed. The member 4 is received in an annular cavity 5 in thecompressor housing 6. The annular member 4 has a shoulder 9 resting on aspring 10 and is pressed by the latter through connecting means 11 andprops or pins 12 against a ring element 13. The latter is coaxial of androtatable on the rotation axis A-B of the compressor.

A packing 7 is interposed between the circumferential surface of theannular member 4 and the opposed cylindrical wall of the cavity 5. Thereis no packing in the clearance between the inner circumference of theannular plate 4 and the casing 6. Since the cavity 5 communicatesrelatively freely with the inlet of the diffuser, the pressure in thecavity 5 cannot noticeably rise above the static pressure at the inletof the diffuser whereas the pressure acting on the relatively largesurface of the member 4 which forms a side wall portion of the diffuseris higher due to the increase of the static pressure in the diffuser.This higher pressure assists the action of the spring 10.

The connecting means 11 do not serve only for transmitting pressure butalso for axially guiding the movement of the annular member 4 andpreventing rotation of theannular member. The elements Ill are axiallyguided in suitable guides 14 in the casing 6. These guides 14 alsoindividually receive spherical ends 15 of the props or pin elements 12,the other ends of the elements 12 being individually provided withspherical heads 15 which individually rest in suitable recesses 16 inthe ring element 13.

A great number of conventional means may be used for rotating the ringelements 13. The drawing shows a worm 17 cooperating with teeth 18 onthecircumference of the ring 13. In order to prevent leakage of theoperating medium of thecompressor into a chamber or cavity 19 of thecompressor casing which accommodates the actuating mechanism foreffecting the axial displacement of the annular member 4 elastic wallmembers or elements, for example, tubular bellows 2t, are provided whichindividually surround the connecting means it and which are connectedwith the annular member 4 and with the stationary compressor housing 6.The connecting means 11 are preferably in the form of pins which areinserted in suitable cylindrical recesses 21 in the annular member 4.

Fig. 2 illustrates the principle of the displacing mechanism accordingto the invention. The upper part of FIG. 2 shows the mechanism in aposition in which the ring 13 is in one of its extreme positions wherebythe prop 12 is at an angle or with respect to the rotation axis AB ofthe compressor. The lower part of FIG. 2 shows the other extremeposition of the ring 13 in which the props 12 are parallel to the axisA-B. The mechanism is so designated that the range of axial displacementof the annular member 4 is equal to the length x. In the upper part ofFIG. 2 the space between the wall 2 and the member 4 amounts to Swhereas in the lower part of FIG. 2 it amounts to S". For moving themechanism from one end position to the other extreme end position thering 13 must travel through a path W. If the angle a=V :L the length Lis changed at first relatively more at a certain reduction of the path Nwhereas the subsequent change of the length L at the subsequentreduction of the path W to zero becomes infinitely small. Due to thisgeometric characteristic of the propping mechanism according to theinvention the progressive reduction of the flow area at a lineardisplacement is avoided which is of advantage when controlling theoutput of a compressor by means of adjusting the width-of the diffuserclearance.

In the modification of the mechanism shown in FIG. 2 the initial strokeof the control mechanism can be adjusted by manipulation of an adjustingscrew 22. The invention is not limited to the mechanism shown anddescribed by way of example. The configuration of the individualelements of the propping or connecting mechanism may, of course, bechanged without departing from the purview of the present invention. Thecompressor may have a plurality of stages.

I claim:

1. A turbocompressor comprising a casing, a rotor, a diffuser arrangedaround said rotor and being, in part, formed by said casing, saiddiffuser having opposite walls, an axially movable annular member placedcoaxial of said rotor and having a surface portion forming part of oneof said walls, said casing having an inside surface portionextendingradially'of the rotation axis of said-rotor, a rotatable ring elementplaced coaxial of said rotor and resting against said surface portion,said casing having a portion interposed between and spaced from saidannular member and said surface portion and having apertures, plurallink means connected to said annular member and to said ring element andextending through said apertures and constructed and arranged so as toaxially displace said annular member for changing the flow area of saiddiffuser upon a rotary motion of said ring element, and axiallyyieldable Wall members fluid tightly connected to and interposed betweensaid annular member and said casing portion and forming a space aroundeach of said link means completely separated from the inside of thecompressor containing the fluid to be compressed.

2. A turbocompressor as defined in claim 1 including spring meansinterposed between said annular member and said casing for pressing saidannular member against said link means and the latter against said ringelement and the said ring element against said surface portion.

3. A turbocompressor as defined in claim 1 in which said link meansinclude connecting means connected to said annular member and slidablyguided in said apertures to move in a direction parallel to the rotationaxis of said rotor for preventing rotation of said annular member upon arotary motion of said ring element.

4. A compressor accordingto'claim 3 wherein said casing has a cavityaccommodating said annular membet and at least a portion of saidconnecting means, said wall members being tubular and placed in saidcavity and individually surrounding said portion of said connectingmeans in said cavity.

5. Acompressor according to claim 3 wherein said link means includes pinelements having spherical ends interposed between and abuttinglyengaging said connecting means and said ring element, said pin elementsbeing placed in a substantiallycylindrical imaginary surface which iscoaxial of the rotation axis of said rotor, said pin elements beingslanted to a greater or lesser degree with respect to said rotation axisupon a rotary motion of said ring element in one or in the oppositedirection for changingthe axial position of said connecting means and ofsaid annular member in said casing.

6. A turbocompressor according to claim 1 wherein said casing has acavity having an annular opening accommodating said annular member, saidopening and said annular member having corresponding oppositecylindrical outside surfaces, packing means being placed between saidcylindrical surfaces.

References Cited in the file of this patent UNITED STATES PATENTS1,322,810 Moody Nov. 25, 1919 2,285,976 Huitson June 9, 1942 2,875,696Zborowski Mar. 3, 1959 2,933,237 Darrow et a1. Apr. 19, 1960 FOREIGNPATENTS 78,038 Germany Nov. 13, 1894 305,214 Great Britain Jan. 29, 1929(Application date)

